Method and apparatus for resizing tools



June 25, 1957 A. s'roLl.

METHOD AND APARATUS FOR REISIZING TOOLS 4 Sheets-Sheet l Filed may e, 195s gg-52. M22/@vm June 25, 1957 A, STOLL 2,796,777

METHOD AND APPARATUS FOR RESIZING TOOLS 4 Sheets-Sheet 2 Filed May 6, 1953 INVENTOR. /VZa/" zzaZ BY MK2 n Y /cLn/ Q June 25, 1957 A. STOLL 2,796,777

METHOD ANO APPARATUS FOR RESIZING TOOLS Fild May 6, 1953 4 Sheets-Sheet I5 225 f5 /fw 1N VENTOR. J HZ eff 5214! Z.

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June 25, 1957 A. s'rou.

METHOD AND APPARATUS FUR RESIZING TOOLS Filed May 6, 1953 4 Sheets-Sheet 4 United States Patent O 2,796,777 METHOD AND APPARATUS FOR RESIZING TOOLS Albert Stoll, Detroit, Mich. Application May 6, 1953, Serial No. 353,313 7 Claims. (Cl. 76-101) This invention relates to methods and apparatus for resizing tools and, more particularly, to an improved method for resizing tools such as punches, reamers, drills, milling cutters and the like, and improved apparatus for performing the same.

Tools of the indicated character become worn and undersized during use, and heretofore, the usual practice has been to grind or otherwise reduce the diameter of worn tools to the next smaller gauge diameter, thereby enabling them to be used as progressively smaller tools. For example, a l/z inch reamer which has become worn or undersized may be ground `to 1%2 inch after which it is sharpened and employed as a 1%2 inch reamer. Such practices have been unsatisfactory where large numbers of such tools are used in production since particular sizes of tools are more widely used than others and there has been a tendency to accumulate the reduced diameter tools. Furthermore, the practice of reducing the diameter of the tools results in excessive waste of the relatively expensive metals from which the tools are made since a relatively large amount of metal must be removed from a tool each time it is reduced in size. In addition, the tool is structurally weakened and loses the desired configuration after it has been reduced several gauge diameters with the result that the tool must be scrapped. Such prior practices may also reduce the hardness properties of the tools and the tools must then be subjected to a heat-treating or hardening operation after they have been reduced in diameter before they may be used in production.

Accordingly, an object of the invention is to overcome disadvantages inherent in such prior practices and to provide an improved method for resizing worn or undersized tools, such as punches, drills, reamers, milling cutters and the like, to their original diameter, thereby increasing the usable life of such tools.

Another object of the invention is to provide an improved method for resizing tools which enables an individual tool to be resized repetitively to its original diameter without loss of its hardness properties, thereby reducing scrap losses to a minimum and obviating the necessity of performing a separate heat-treating operation.

Another object of the invention is to provide an improved method for resizing tools which reduces the number of operations required to restore a worn or undersized tool to its original diameter.

Another object of the invention is to provide an improved method for resizing tools which reduces the amount of waste material and the amount of time, labor and expense to a minimum.

Another object of the invention is to provide improved apparatus which enables the quantity resizing of worn or undersized tools and which is strong and rugged in construction, economical to manufacture andassemble, efficient and reliable in operation.

Still another object of the invention is to provide improved apparatus for carrying out the method of the present invention wherein improved means -Vare `provided for 'ice 2 controlling the temperature of the tools during the resizing operation.

Yet another object of the invention is to provide lmproved apparatus for performing the method of the present invention which enables worn or undersized tools to be resized with accuracy, uniformity and precision.

The above as well as other objects and advantages of the present invention will become apparent from the following description, taken in conjunction with the accompanying drawings wherein:

Figure l is an elevational view of `a piercing punch in the original or unworn condition.

Fig. 2 is a fragmentary view of a punch in the worn or undersized condition;

Figs. 3 through 5 are fragmentary views of the punch illustrated in Fig. 2 after progressive steps in a resizing operation utilizing the method of the present invention;

Fig. 6 is a vertical, sectional view of apparatus constructed in accordance with one embodiment of the present invention',

Fig. 7 is a plan view of a portion of the structure shown in Fig. 6, taken on the line 7-7 thereof;

Fig. 8 is a fragmentary plan view of apparatus constructed in accordance with another embodiment of the invention;

Fig. 9 is a fragmentary, elevational view of a worn or undersized reamer;

Fig. l0 is a side elevational view, with portions in Section and other portions broken away, of apparatus constructed in accordance with another form of the present invention and showing the undersized reamer positioned therein preparatory to resizing;

Fig. ll is a fragmentary top plan view of the structure illustrated in Fig. l0, taken on the line 111l thereof;

Fig. l2 is a fragmentary, sectional, side elevational view of the structure illustrated in Fig. 10, taken on the line 12-12 thereof;

Fig. 13 is an enlarged, fragmentary view of a portion of the structure illustrated in Fig. ll, taken on the line 13 -13 thereof;

Fig. 14 is a fragmentary end view of the structure illustrated in Fig. 13;

Fig. l5 is a greatly enlarged end View of the reamer illustrated in Fig. 9 showing the same positioned intermediate the rotatable spherical members prior to the resizing operation; and

Fig. 16 is a greatly enlarged end view of the reamer subsequent to the resizing operation.

Referring to the drawings, and more particularly to Fig. l, a piercing punch, generally designated 20, is shown, although it will be understood that the present invention is applicable to other types of tools, as will be hereinafter described in greater detail. A punch of the type illustrated includes a body portion 22, one end of which is adapted to fit into a quill or other holding device secured to a conventional punch plate (not shown). A groove 24 is provided to facilitate locking the piercing punch in the quill while the opposite end of the body 22 is enlarged to form a head 26, the face 27 of which is beveled, as at 28, to reinforce the edge of the punch.

The portion 30 of the body adjacent the head 26 may also be reduced in diameter to provide clearance for the portion of the body which enters the workpiece.

As shown in Fig. 2, the head 26 of the punch becomes worn and undersized as the punch is used and after a certain amount of use, the apertures formed in the workpiece are no longer within acceptable tolerance limits. The present invention provides means for restoring the tool to its original gauge diameter with a minimum of waste material and without substantial loss in the hardness properties of the tool.

In general, the method of resizing "a worn or undersized tool comprises the steps of first heating at least the undersized portion of the tool to an elevated temperature which will permit plastic deformation without disturbing the room temperature hardness of the particular metal from which the tool is made; aligning the tool with a rotatable member of greater hardness than the tool; and forcing the undersized portion of the tool against the rotatable member to cause the metal forming such undersized portion to flow radially of the axis of the tool to a diameter at least equal to the original or desired diameter, while maintaining the temperature below the temperature where permanent softening takes place.

The present invention is particularly adapted for use in resizing tools made of alloy steels, as for example, highspeed steel, but it will be understood that the present invention is equally applicable to tools made from a metal which will return to its approximate original hardness after being heated to an elevated temperature and which, at the elevated temperature, becomes suiiciently malleable to tolerate deformation, without fracture, such as is required to increase the diameter of a tool which may be worn or undersized. Some materials, such as most of the high-speed steels, can be heated to relatively high temperatures for short lengths of time without lowering the room temperature hardness. If kept at these elevated temperatures for a considerable length of time (the higher the temperature, the shorter the time) the room temperature hardness drops off. Therefore, under certain conditions of operation involving rapid manipulation of the metal, higher temperatures can be used with correspondf ing benefits from the malleability standpoint.

By lirst heating the tool to an elevated temperature where maximum malleability of the metal forming the tool is obtained during the swaging operation, the forces required to cause the metal to flow radially of the axis of the tool are reduced and the wear on the rotatable upsetting or swaging members is also reduced. At the same time, the necessity of a separate heat-treating operation is obviated as long as the temperature of any part of the tool does not reach the permanent softening temperature, since the tool will retain its original hardness properties upon cooling to ambient temperatures.

In the preferred embodiments of the invention, both the tool to be resized and the rotatable upsetting members are immersed in a heated fluid bath prior to the upsetting or swaging operation in order to insure even heating of the tool and to prevent spot-cooling of the tool as it comes into contact with the rotatable upsetting members, thereby preventing the occurrence of high thermal stresses which may fracture the metal. At the same '.5

time, the lluid bath removes the excess heat generated during the upsetting operation and prevents the temperature of the tool from rising above the permanent softening temperature. The particular fluid bath which may be employed is not critical for the purposes of the present invention and may take the form of a liquid bath or a gaseous bath. It is preferred to utilize a relatively inert bath so that the ingredients thereof will not react with the metal from which the tool is made during the upsetting operation. For example, a liquid bath may include a neutral salt or it may take the form of a lead bath. Similarly, a gaseous bath may utilize an inert gas or air as the fluid. When a liquid bath is utilized, the liquid also functions to lubricate the rotatable members, thereby reducing the wear on such members.

One embodiment of the invention is particularly adapted to resize worn or undersized piercing punches of the type previously described. The heated piercing punch is immersed in the heated bath and the head of the punch is aligned with the center of a group of upsetting members which are rotatably supported by a retaining member fixed in the bath. The tool is then rotated and at the same time axial pressure is applied to the tool so that the head of the tool is forced against the rotatable upsetting members which cause the metal forming the head of the punch lill to flow radially of the axis of the tool. The combined axial and rotary movement of the punch enables the rotatable upsetting members to wear evenly and at the same time an even radial ow of the metal in the head of the punch is achieved. In this embodiment of the invention, sulicient pressure is applied to the tool to upset the head thereof to a diameter greater than the original or desired diameter so that after the upsetting operation, the head of the tool is of the configuration shown in Fig. 4.

It has been found that when the head of the undersized punch is badly worn so that the beveled marginal portion 28 of the face 27 is considerably rounded, it is desirable to flatten the face 27 of the head prior to the upsetting operation so that the marginal portion of the face of the head will be beveled by the rotating members, during the upsetting operation, as brought out in Fig. 4.

After the upsetting operation, the tool is allowed to cool to room temperature and an actual increase in the hardness properties may be obtained as a result of the work performed on the undersized portion during the upsetting operation.

After the tool has cooled to ambient or room temperature, it is machine finished, as by grinding, to the original or desired diameter` By varying the amount of axial pressure that is applied to the tool as it is forced against the rotatable upsetting members, and the speed of rotation during the upsetting of the tool head, the diameter of the head may be controlled within relatively close limits so that it is necessary to remove only a minimum amount of metal by grinding, in order to achieve the desired diameter.

The above described embodiment of the invention enables the quantity resizing of piercing punches with a minimum expenditure of time, labor and expense and obviates the necessity of a separate heat-treating operation after the resizing operation. The punch may be rcsized repetitively without loss of its original hardness properties and it has been found that a resized punch may be used for substantially the same number of piercing operations as when new. Thus, the number of piercing operations which the tool is capable of performing is substantially multiplied and the useful life of the tool is materially increased.

Illustrative apparatus for performing the above described method is shown in Figs. 6 and 7 and is comprised of a base 32 having an integral, centrally disposed portion 34 projecting upwardly therefrom. The upper end of the upwardly projecting portion 34 is reduced in diameter so as to form an abutment 36 adapted to support a hollow outer housing 38 having vertically disposed, radially spaced inner and outer walls 40 and 4l and horizontally disposed, vertically spaced walls 42 and 43 detining a chamber 44. The chamber 44 is filled with a suitable heat insulating material, such as asbestos, and is provided with a fiat, ring-shaped closure member 46, the marginal portion of which is provided with a depending flange 48 adapted to lit over the outer wall 41 of the chamber. The inner portion of the closure member 46 engages a cup-shaped member 50 which functions as a container for the Huid bath.

An integral, centrally disposed tubular portion 52 projects downwardly from the cup-shaped member 50 and is adapted to be received in the bore 54 of the upwardly projecting portion 34, the lower end of the tubular perA tion 52 resting on the base 32. A hub 56 projects upwardly into the central portion of the cup-shaped member 50 and is provided with a recess 58 adapted to receive a ball raceway block 60 which is preferably formed of chromium carbide, tungsten carbide, or other relatively hard and heat resistant material. The block 60 is provided with a centrally disposed ring-shaped groove 62 which serves as a receway for a plurality of spherical member 64 which are preferably made of the same material as the block 60.

A conventional chuck 66 is aligned with the center of the group of spherical members 64, the chuck being mounted on a rotatable and axially movable spindle 68 which in turn may be driven by any suitable means, such as an electric motor (not shown).

For the purpose of heating the bath, a. heating element 70 is mounted below the cup-shaped member 50, the heating element being retained by a nut 72 which threadedly engages the upper end portion of the depending tubular portion 52. A power line 74 is electrically connected to the heating element 70 by any suitable means, such as by a terminal 76 which engages a post 78 and is retained by a nut 80. The power line 74 passes through a radially extending passageway 82 provided in the housing 38 and the power line is connected to a suitable source of potential through a thermostatc switch element (not shown) so that the bath may be maintained at any desired temperature.

In the operation of this form of the invention, the punch to be resized is heated to a temperature near, but below, the permanent softening temperature of the metal from which the tool is made and the tool is positioned in the chuck 66. The heating element 70 is energized so as to maintain the bath in the cupshaped member 50 at a temperature near, but below, the permanent softening temperature of the tool and since the block 60 and the spherical members 64 are disposed in the bath, such members are also heated to the temperature of the bath, thereby preventing spot-cooling of the punch as it comes into :contact with the spherical members. The spindle 68 is then rotated and at the, same time moved downwardly so that the head 26 of the punch is forced against the spherical members 64 while rotating. Axial pressure is then applied to the punch through the spindle 68 and the chuck 66 so that the head is upset by the rotatable spherical members 64, and assumes the configuration shown in Fig. 4.

After the punch has been upset to a diameter equal to or slightly greater than the desired or original diameter, the spindle 68 is moved upwardly and the punch removed from the chuck 66. The punch 20 is then allowed to cool to room temperature after which the head 26 may be ground to the desired or original diameter, as shown in Fig. 5.

Another embodiment of the invention, which is particularly adapted to obviate the necessity of a separate grinding operation is illustrated in Fig. 8. In this embodiment of the invention, a mounting block, generally designated 84, is provided having an outwardly projecting central portion 86 which, in the preferred embodiment illustrated, is shaped in the form of a trapezoid. The block 84 is also provided with integral, angularly extending arms 88 and 90 which project outwardly on opposite sides of the central portion 86 in spaced relationship thereto so as to define a pair of slots 92 and 94. The slots 92 and 94 are adapted to accommodate rollers 96 and 98, respectively, the rollers preferably being formed of chromium carbide, tungsten carbide or other relatively hard and heat resistant material. The rollers 96 and 98 are mounted on shafts 100 and 102, the outer end portions of which are journaled for rotation in axially adjustable sleeve bearings 104 and 106 while the inner end portions of the shafts 100 and 102 are journaled in recesses 108 and 110 provided in the central portion 86 of the block 84. The sleeve bearings 104 and 106 threadably engage apertures 112 and 114 in the arms 88 and 90, respectively, and are retained therein by suitable checknuts 116. The inner ends of the sleeve bearings also function as abutment stops so that the spacing be tween the rollers 96 and 98 may be varied by moving the sleeve bearings inwardly or outwardly in the apertures 112 and 114. With such a construction, the diameter of the head of the punch may be accurately controlled and the punch may be resized to the desired diameter, thereby obviating the necessity of a separate grinding operation.

The outer end portion 118 of each roller is cylindrical and in integrally joined to the cylindrical inner end portion 120, which is of a smaller diameter than the outer end portion, by a central portion 122 which is preferably shaped in the form of a truncated cone.

In this form of the invention, the punch to be resized is heated prior to the resizing operation by circumferentially spaced gas burners 124 which are positioned outwardly from the rollers 96 and 98 and extend radially Vinward of the axis of a chuck 126. It will be understood, however, that the block 84 may be mounted in a heated fluid bath in the manner hereinbefore described.

In the operation of this form of the invention, the punch to be resized is mounted in the chuck 126 which in turn is fixed to a rotatable spindle (not shown). The head 26 of the punch is initially positioned intermediate the burners 124 and rotated and heated to a temperature near, but below the permanent softening temperature of the metal forming the tool. While in the heated condition, the tool is simultaneously rotated and moved axially so as to bear against the rollers 96 and 98 which upset the head as axial pressure is applied to the punch. The relative angular positioning of the cylindrical portions of the rollers confine the tapered portion 28 of the head while the truncated conical portions 122 of the rollers confine the side portions of the head to the desired diameter. Since the rollers 96 and 98 may be moved outwardly with respect to each other, the diameter of the head 26 of the punch may be controlled accurately and a separate grinding operation is not necessary.

Another embodiment of the invention, particularly adapted for use in resizing drills, reamers, milling cutters and the like is illustrated in Figs. 9 through 16 and is comprised of a housing, generally designated 130, shaped in the form of a parallelepiped. The housing 130 is provided with a horizontally disposed, substantially rectangular base 132 which is adapted to rest on the oor or other fixed support and spaced substantially parallel side walls 134 and 136 are fixed to the base, as by welding or the like, so as to project upwardly therefrom, the edge portions of the side walls being joined by spaced end walls 138 and 140. The upper end portion of the housing 130 is closed by a displaceable closure plate 142 having depending pins, such as 144, projecting downwardly there from which engage the walls of the housing and prevent lateral movement of the closure member 142 relative to the housing.

A horizontally disposed plate 146 extends in parallel spaced relationship to the base 132 and thc edge portions of the plate 146 are welded or otherwise fixed to the Walls of the housing so as to divide the housing into chambers 148 and 150.

A centrally disposed muie, generally designated 152, is mounted in the chamber 148. The mule 152 is preferably formed of tirebrick or other heat resistant material and defines a horizontally disposed passageway 154 which is open at each end.

For the purpose of heating the muie, a plurality of electrical resistance elements 156 are embedded in the walls thereof so as to encompass the passageway 154, the resistance elements being electrically connected to a suitable source of potential by conductors 158 and 160 and controlled by suitable thermostatic switch elements (not shown) so that the temperature in the mufile may be maintained within any desired range. The mufe 152 is encased in a casing 162 having top and bottom walls 164 and 166 joined by spaced side walls 168 and 170 and end walls 172 and 174. The edge portions of the bottom wall 166 terminate in outwardly spaced relationship with respect to the side and end walls and the lower surface of the bottom wall 166 rests on the upper surfaces of a plurality of heat insulating blocks 176 which are pref erably formed of firebrick or the like. The blocks 176 in turn are supported by horizontally disposed plate 146. In order to further reduce the heat losses, the chamber 148 may be filled with flaked mica or other heat insulation material.

The end portions of the passageway 154 in the muflle are extended through oppositely disposed walls of the casing 162 and housing 130 by means of axially aligned `tubular members 178 and 180, the inner end portions of which are fixed to the walls 172 and 174 of the casing while the outer end portions are fixed to the walls 138 and 140 of the housing.

A centrally disposed, vertically extending passageway 182, adapted to receive the tool to be resized, is formed in the mufile 152 and extends through the chamber 148,

intersecting the axis of the passageway 154 at substantially right angles. The lower end portion of the passageway 182 is defined by a bushing 184, the upper end of which is fixed to the bottom wall 166 of the casing 162 while the lower end of the bushing is provided with a radially extending flange 186 which is secured to the plate 146. The upper end portion of the passageway 182 is defined by a tube 188, the lower end of which is fixed to the upper wall 164 of the casing 162 while the upper end of the tube abuts the closure plate 142. A transparent, heat resistant member 190 is fitted in a centrally disposed portion 192 in the plate 142 and enables the visual inspection of the resizing operation through the passageway 182.

A tool actuating fixture, generally designated 194, is

mounted in the chamber 150 and is comprised of a mounting block 196 having transversely extending flanges 198 thereon which slidably engage the inner surface 200 of the wall 138 while an outwardly projecting stud 202 projects through a slot 204 in the wall 138 and threadedly engages a locking member 206 having handle means 208 projecting outwardly therefrom. Such a construction enables the block 196 to be moved vertically relative to the base 132 and locked in a selected adjusted position.

A fioating tool holder 210 is aligned with the vertical axis of the passageway 182, the upper portion of the tool holder 210 having a recess 212 therein adapted to receive the shank of a tool, such as a reamer 213. A setscrew 214 threadably engages a radially extending aperture in the holder 210 and serves to releasably lock the tool in the holder. The lower portion of the tool holder includes upper and lower ball bearing races 216 and 218 having ball bearings 220 interposed therebetween which enable the tool to rotate freely about its vertical axis. The lower race 218 is fixed to `a quill 222 which is vertically movable through a conventional rack and pinion actuated by a capstan wheel 224. With such a construction, it will be appreciated that the tool may be moved axially in the passageway 182 by manually rotating the capstan wheel 224 and that the tool will be free to rotate f about its longitudinal axis through the agency of the ball bearing connection between the tool holder 210 and the quill 222.

A pair of guide blocks 226 and 228, which are preferably formed of chromium carbide, tungsten carbide, or

other relatively hard and heat resistant material are mounted in the passage 154 on opposite sides of the passageway 182. The guide blocks 226 and 228 are provided with parallel grooves 230 and 232, the longitudinal axes of which extend substantially parallel with the axis of the passageway 182 and are adapted to accommodate spherical members 234 and 236, respectively. The spherical members 234 and 236 are preferably formed of the same material as the guide blocks 226 and 228 and the spherical members are retained by plates 238 and 240 which are fixed to the ends of the blocks 226 and 228, the plates being provided with elongated slots 242 and 244. the diameter of which is slightly less than the diameter of the spherical members 234 and 236 so that the periphery of the spherical members projects through the slots. The block 226 is mounted in `a fixed position in the passageway 154, and as best seen in Fig. 14, the block 226 is provided with a tongue 246 adapted to be received in a groove 248 provided in the inner end of an elongated bar 250. The outer end of the bar 250 is Welded 0r otherwise rigidly fixed to a mounting plate 252 secured to the wall 140 of the housing by bolts 254.

The block 228 is movable relative to the block 226 and is provided with a tongue 256 which is fitted in a groove 258 provided in the inner end of an elongated bar 260. The outer end portion of the bar 260 is slidably mounted in a bearing member 262 which is formed in the shape of a channel having horizontally disposed flange portions 264 and 266 and a vertically extending web portion 268. A vertically extending closure plate 270 is secured to the edges of the fiange portions 264 and 266 by setscrews 272 and the inner end portion of the bearing member 262 is fixed to a mounting plate 274, as by welding or the like. The mounting plate in turn is secured to the wall 138 of the housing by bolts 276.

In order that the block 228 may be reciprocated relative to the block 226 so that pressure may be applied to the tool to be resized, a reciprocating frame, generally designated 278, is provided and is comprised of end pieces 280 and 282 which extend transversely of the housing in spaced relation thereto and are joined by link arms 284 and 286 which are fixed to the ends of the end pieces 280 and 282 by screws 288. The central portion of the end piece 282 is snugly fitted in an aperture 290 in the bar 260 and the outer end portions of the end piece project outwardly through aligned slots 292 and 294 which are provided in the web portion 268 of the bearing member 262 and the closure plate 270. At a position near. but spaced from, the end piece 280 the link arms 284 and 286 are provided with elongated slots 296 and 298 adapted to slidably accommodate headed pins 300 and 302 which extend through the slots 296 and 298, respectively, and threadably engage the walls 134 and 136 of the housing so as to slidably support the frame 278. An elongated screw 304 projects through and threadably engages the end piece 280, the outer end portion of the screw 304 being provided with a hand wheel 306 which is retained by a nut 308 which facilitates the manual rotation of the screw. The inner end portion of the screw is journaled for rotation in a recess 310 provided in the mounting block 252. With such a construction, when the screw 304 is rotated in one direction, the end piece 280 moves outwardly relative to the wall 140 of the housing thereby causing the link arms 284 and 286 to move the end piece 282 inwardly toward the wall 138. The movement of the end piece 282 forces the bar 260 and the block 228 inwardly toward the block 226 so that pressure may be applied to the tool which is being resized through the spherical members 234 and 236.

In the operation of this form of the inventio-n, the heating elements 156 are energized so as to heat the mufiie 152 to the desired temperature which is near, but below, the permanent softening temperature of the metal forming the tool to be resized. The tool, as for example, a reamer, is then heated to a similar temperature and positioned in the holding member 210. The capstan wheel 224 is then rotated so as to move the tool upwardly into the passageway 182 so that the spherical members 234 and 236 are positioned in the flutes between adjacent teeth of the tool, as shown in Fig. 15. The hand wheel 306 is then rotated so that the spherical members 234 and 236 are forced against the tool by the pressure applied to the spherical members 234 and 236 as a result of the movement of the frame 278 to the left, as viewed in Fig. l0, and the consequent transmission of the pressure through the bar 260 and the block 228. The tool is then moved upwardly in the passageway 182 so that the spherical members 234 and 236 roll in the grooves 230 and 232 of the guide blocks 226 and 228 and are forced against the flanks of adjacent teeth of the tool for substantially the entire length thereof to cause the metal forming the teeth to flow outwardly, as viewed in Fig. 16. The tool is then reciprocated in the passageway 182 while increased pressure is applied through the spherical members 234 and 236 to cause the metal forming the cutting teeth of the tool to ow outwardly to any desired diameter. The tool is then indexed so that the spherical members engage adjacent teeth of the tool and the operation is repeated until all of the cutting teeth of the tool have been enlarged to the desired diameter after which the tool may be removed from th-e holder 210 and allowed to cool to room temperature. The tool may then be ground to the original or the desired diameter and sharpened in the conventional manner.

While this form of the invention has been shown as applied to a straight fluted reamer, it will be understood that the invention is equally applicable to spiral luted reamers, twist drills, taps, milling cutters and the like, and it will also be understood that while preferred embodiments of the invention have been shown and described, various changes and modifications may be made without departing from the spirit of the invention.

What is claimed is:

1. The method of enlarging a hardened tool, having an undersized portion, without substantial loss in the hardness properties thereof, which comprises the steps of heating the tool to an elevated temperature below the permanent softening temperature but sufcient to increase the malleability of the undersized portion, immersing the undersized portion in a fluid bath heated to a corresponding temperature, simultaneously rotating the tool and applying pressure thereto to force the undersized portion against a group of rotatable members so as to cause the undersized portion to flow outwardly from the axis of the tool to a dimension greater than the desired dimension, allowing the tool to cool, and thereafter machine finishing the upset portion to the desired dimension.

2. The method of resizing the undersized portion of a hardened tool to its original diameter without substantial loss in the hardness properties thereof, which comprises the steps of immersing the undersized portion of the tool in a fluid bath heated to an elevated temperature below the permanent softening temperature but sufficient to increase the malleability of the undersized portion, simultaneously rotating the tool and applying axial pressure thereto to force the undersized portion against a plurality of rotatable members to cause the undersized portion to flow radially of the axis of the tool to a diameter greater than the original diameter, allowing the tool to cool, and thereafter machine finishing the upset portion to the desired diameter.

3. The method of resizing the undersized portion of a hardened tool to its original diameter without substantial losses in the hardened properties thereof, which comprises the steps of heating the tool to an elevated temperature below the permanent softening temperature, aligning the tool with a rotatable member of greater hardness than the tool, immersing the tool in a uid bath heated to a corresponding temperature, simultaneously rotating the tool and forcing the undersized portion thereof against the rotatable member so as to cause the undersized portion to flow radially of the axis of the tool to a predetermined diameter.

4. The method of resizing the undersized portion of a hardened tool to a greater diameter without substantial losses in the hardness properties thereof, which comprises the steps of heating the tool to an elevated temperature below the permanent softening temperature, aligning the tool with a plurality of rotatable members of greater hardness than the tool, immersing the tool in a uid bath heated to a corresponding temperature, simultaneously rotating the tool and applying axial pressure thereto so as to force the undersized portion against the rotatable members and `cause the undersized portion to tiow radially of the axis of the tool to a predetermined diameter.

5. The method of resizing the undersized portion of a hardened tool to a greater diameter without substantial losses in the hardness properties thereof, which comprises the steps of heating the tool to an elevated temperature below the permanent softening temperature, immersing the tool in a fluid bath heated to a corresponding ternperature, positioning the tool intermediate a plurality of rotatable members of greater hardness than the tool, applying pressure to the undersized portion through the rotatable members to cause the undersized portion to iiow outwardly of the longitudinal axis of the tool, and reciprocating the tool while maintaining the pressure thereon.

6. The method of enlarging the undersized portion of a hardened tool to a greater diameter without substantial losses in the hardness properties thereof, which comprises the steps of heating the tool to an elevated temperature below the permanent softening temperature, immersing the tool in a fluid bath heated to a corresponding temperature, positioning the tool intermediate a plurality of rotatable members of greater hardness than the tool, applying pressure to the undersized portion through the rotatable members to cause the undersized portion to ow outwardly of the longitudinal axis of the tool, reciprocating the tool axially while maintaining the pressure thereon, and successively increasing the pressure and reciprocating the tool axially while maintaining the pressure thereon.

7. The method of enlarging the undersized portion of a hardened tool to a greater diameter without substantial losses in the hardness properties thereof, which comprises the steps of heating the tool to an elevated temperature below the permanent softening temperature, immersing the tool in a tiuid bath heated to a similar temperature, positioning the tool intermediate a plurality of rotatable members of greater hardness than the tool, applying pressure to the undersized portion through the rotatable members to cause the undersized portion to liow outwardly of the longitudinal axis of the tool, reciprocating the tool axially while maintaining the pressure thereon, successively increasing the pressure and reciprocating the tool axially while maintaining the pressure thereon so as to enlarge the undersized portion to a diameter greater than the desired diameter, and thereafter reducing the enlarged portion to the desired diameter.

References Cited in the le of this patent UNITED STATES PATENTS 1,096,009 Ayres May 12, 1914 1,246,750 Joy Nov. 13, 1917 1,277,770 Thiele Sept. 3, 1918 1,332,481 Ayres Mar. 2, 1920 1,353,535 Wercombe Sept. 21, 1920 1,443,953 Hoenscheid Feb. 6, 1923 1,608,079 Wurster Nov. 23, 1926 2,164,569 Christi-nan July 4, 1939 2,223,799 Annen Dec. 3, 1940 2,362,779 Stevens Nov. 14, 1944 2,418,338 Dworkowski et al Apr. 1, 1947 2,467,302 Forster et al Apr. 12, 1949 2,541,455 Anderson Feb. 13, 1951 

